Semiconductor manufacturing apparatus for manufacturing a semiconductor device having a high-K insulating film, and a method for manufacturing the semiconductor device

ABSTRACT

Provided is a semiconductor manufacturing apparatus including: a container in which a processing chamber is installed; a stage installed in the processing chamber and configured to hold a semiconductor substrate; a gas supply line configured to supply reactive gas to the processing chamber; and a vacuum line configured to exhaust the processing chamber, wherein the semiconductor substrate includes a high-k insulating film, and as the reactive gas, mixed gas including complex-forming gas forming a volatile organometallic complex by reacting with a metal element included in the high-k insulating film and complex stabilizing material gas that increases stability of the organometallic complex is supplied.

CLAIM OF PRIORITY

The present application claims priority from Japanese patent applicationJP 2017-085910 filed on Apr. 25, 2017, the content of which is herebyincorporated by reference into this application.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a semiconductor manufacturing apparatusfor manufacturing a semiconductor device having a high-k insulatingfilm, and a method for manufacturing the semiconductor device.

2. Description of the Related Art

The demands for miniaturization, higher speed and performance, and lowpower consumption of the state-of-the-art semiconductor devices continueto grow, and the use of a metal oxide film material having a specificdielectric constant higher than that of a silicon oxide (SiO₂) film orsilicon oxynitride (SiON) film is getting increased as a gate insulatingfilm becomes thinner. For example, studies are in progress for applying,to the gate insulating film, a high-k metal oxide film material, whichinclude elements such as hafnium (Hf), zirconium (Zr), tantalum (Ta),titanium (Ti), yttrium (Y), lanthanum (La), and lanthanides as rareearth and include metal oxides hard to reduce at an interface withsilicon (Si) at high temperature or composite oxides of these metals andsilicon (Si).

However, it is not always easy to perform fine processing on thesehigh-k insulating film materials. For example, it is known that the filmquality deteriorates due to wet treatment of a fine processing processof a lanthanum oxide film (La₂O₃), in particular, a photolithographyprocess. Various new technologies have been proposed for that problem.For example, JP 2009-252895 A discloses a technology for preventing alanthanum film from deteriorating due to the wet treatment process byintroducing a multilayer structure into the gate insulating film. Inaddition, JP 2015-191922 A discloses a technology of performing dryetching processing on a metal oxide including hard-to-etch materials byusing a reactive ion etching method using gas including borontrichloride (BCl₃).

Steven George, Younghee Lee, Jaime DuMont, Nicholas Johnson and AmyMarquardt “Thermal Atomic Layer Etching Using Sequential, Self-LimitingFluorination and Ligand-Exchange Reactions” (Proceedings of 38thInternational Symposium on Dry Process, Nov. 21-22, 2016, pp 15-16) asan approach different from the JP 2009-252895 A and JP 2015-191922 Adiscloses a technology of performing etching processing on an insulatingfilm by fluorinating a surface of the insulating film material,converting the insulating film into a volatile organometallic complex bya ligand-exchange reaction between metal fluoride and an organiccompound, and then evaporating and removing the volatile organometalliccomplex.

SUMMARY OF THE INVENTION

In the case of performing fine dimensional pattern processing in the wettreatment, there is a possibility that the pattern may collapse due to asurface tension of wet treatment liquid or rinse liquid. In contrast, ina reactive ion etching (RIE) technology using a gas including ahalogen-based component such as BCl₃, since the dry etching is used, itis possible to avoid the problem of the pattern collapse, but since avapor pressure of the halide of the metal element constituting thehigh-k insulating film material is low, it is not easy to secure asufficient etching rate and there is also a need to improve an etchingselective ratio with silicon (Si).

Since the method disclosed in Steven George, Younghee Lee, Jaime DuMont,Nicholas Johnson and Amy Marquardt “Thermal Atomic Layer Etching UsingSequential, Self-Limiting Fluorination and Ligand-Exchange Reactions”(Proceedings of 38th International Symposium on Dry Process, Nov. 21-22,2016, pp 15-16) also uses the dry etching technology, it has been shownthat it is possible to etch a hafnium oxide film (HfO₂) which is one ofthe high-k insulating film materials. Practically, however, a dryetching technology capable of etching the high-k insulating filmmaterial at a higher speed is required.

The inventor found thermal dry etching processing of converting a high-kinsulating film into a volatile organometallic complex and thenevaporating or subliming the volatile organometallic complex to beremoved by studying etching chemistry of a gate insulating filmmaterial, and as a result, has reached the present invention. Since thedry etching is used, defects of the fine pattern collapse due to the wettreatment liquid do not occur, and since the volatile organometalliccomplex having a high vapor pressure is used, the etching can beperformed at high speed.

A semiconductor manufacturing apparatus, including: a container in whicha processing chamber is installed; a stage installed in the processingchamber and configured to hold a semiconductor substrate; a gas supplyline configured to supply reactive gas to the processing chamber; and avacuum line configured to exhaust the processing chamber, in which thesemiconductor substrate includes a high-k insulating film, and as thereactive gas, mixed gas including complex-forming gas forming a volatileorganometallic complex by reacting with a metal element included in thehigh-k insulating film and complex stabilizing material gas thatincreases stability of the organometallic complex is supplied.

Further, a second aspect of the invention is a method for manufacturinga semiconductor device, the method including: placing, in a processingchamber, a semiconductor substrate on which a mask layer having apredetermined pattern shape is formed on a high-k insulating film;desorbing gas or a foreign matter adsorbed on a surface of thesemiconductor substrate; supplying reactive gas to the processingchamber in a state where a temperature of the semiconductor substratefalls below a predetermined temperature; stopping the supply of thereactive gas and heating the semiconductor substrate; and vaporizing anorganometallic complex generated by reacting with a metal elementincluded in the high-k insulating film and exhausting the vaporizedorganometallic complex from the processing chamber, wherein the reactivegas is mixed gas including complex-forming gas forming theorganometallic complex by reacting with the metal element included inthe high-k insulating film and complex stabilizing material gas thatincreases stability of the organometallic complex.

It is possible to selectively etch the high-k insulating film at highspeed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a semiconductor manufacturing apparatus(processing portion);

FIG. 2 is a diagram for describing an operation principle of avaporizer;

FIG. 3 is a schematic diagram of the semiconductor manufacturingapparatus (including peripheral units).

FIG. 4 is an example of a cross-sectional view of a semiconductorsubstrate;

FIG. 5 is a diagram schematically illustrating an example of a surfacetemperature cycle of the semiconductor substrate in an etching process;

FIG. 6 is a diagram illustrating an example of a material for complexstabilizing material gas;

FIG. 7 is a diagram for describing an action of the complex stabilizingmaterial gas; and

FIG. 8 is a diagram illustrating a reaction rate of mixed etching gasand a substance.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates a semiconductor manufacturing apparatus (processingportion) of the present embodiment. The semiconductor manufacturingapparatus includes a container 10 configuring a vacuum chamber, in whicha processing chamber 11 is installed in the container 10 and a waferstage 12 for holding a semiconductor substrate (wafer) 1 is installed inthe processing chamber 11. A vacuum line 13 and a gas supply line 15 areconnected to the container 10, and the vacuum line 13 and the gas supplyline 15 are each provided with an opening/closing valve 14 and anopening/closing valve 16. By this configuration, an internal pressure ofthe processing chamber 11 can be controlled by controlling and adjustinga vacuum system and a gas supply system. Further, the semiconductorsubstrate 1 outside the processing chamber 11 is conveyed into theprocessing chamber 11 or the semiconductor substrate 1 inside theprocessing chamber 11 is conveyed out of the processing chamber 11,through a wafer conveyance port 20 installed in the container 10.

Although not illustrated, a heater for heating or a heating unit such asa halogen lamp and a cooling unit such as a chiller pipe for cooling areinstalled in the semiconductor manufacturing apparatus, and temperaturesof the container 10, the processing chamber 11, and the wafer stage 12are adjusted such that a surface temperature of the semiconductorsubstrate 1 falls within a proper range. Similarly, various functionalunits or various sensors used for manufacturing a semiconductor device,for example, a plasma generation source, an external network connectiondevice, an uninterruptible power supply, a pressure gauge, athermometer, a flow meter or the like are installed as necessary.

In the semiconductor manufacturing apparatus, a wafer chucking mechanismfor certainly grasping the wafer which is being etched is installed inthe wafer stage 12. According to the present embodiment, anelectrostatic chuck for electrostatically chucking the wafer can beapplied. In the case of an electrostatic adsorption method, a densitydistribution of plasma generated in the processing chamber may beaffected by an electric field generated near a wafer surface. Althoughthe etching principle of the present embodiment will be described later,unlike an RIE method, ion species and radical species in the plasma arenot used for processing an insulating film, and the generation of theplasma is limited to, for example, a pretreatment process such asremoval of adsorbed gas on the surface. For this reason, there is norisk of affecting processing accuracy of the insulating film even if theelectrostatic chuck is applied. Any of a coulombs force type, a gradientforce type, and a Johnsen-Rahbek type is selectively applied accordingto a kind and a content of a material to be etched and etchingprocessing. It may be other chucking mechanisms such as a mechanicalchuck.

A chemical liquid tank 31 for storing a chemical liquid 30 as a rawmaterial of etching gas and a vaporizer 32 for vaporizing the chemicalliquid 30 are connected to the gas supply line 15. The chemical liquid30 is a mixed raw material liquid for generating mixed etching gasincluding complex-forming gas which is a component for converting ahigh-k insulating film formed on the wafer 1 into a volatileorganometallic complex and complex stabilizing material gas which is acomponent for increasing stability of the volatile organometalliccomplex. The chemical liquid 30 is sent to the vaporizer 32 to generatereactive gas (hereinafter referred to as mixed etching gas) including amixture of the above-described plurality of functional gas components.The chemical liquid 30 at least includes a raw material for thecomplex-forming gas and a raw material for the complex stabilizingmaterial gas.

In the present embodiment, the mixed chemical liquid 30 mixed with thekind of raw material gases is introduced into the single vaporizer 32,and plural components are simultaneously gasified to generate the mixedetching gas and are introduced into the processing chamber 11 throughthe single gas supply line 15. The reason will be described later. Asthe structure of the vaporizer 32, for example, a bubbling type can beapplied. By using a vaporizer having a simple structure, it is possibleto reduce the cost of the semiconductor manufacturing apparatus andminimize the installation area. In addition to the bubbling type, aknown vaporizer such as a direct injection type, an ultrasonicatomization method, or a combination thereof can be used.

By appropriately selecting the combination of the complex-forming gasand the complex stabilizing material gas and the operating condition ofthe vaporizer 32, the supply of the mixed etching gas can be realized bythe gas supply line 15 having a simple structure. The operationprinciple of the unified vaporizer 32 will be described with referenceto FIG. 2. In FIG. 2, a horizontal axis represents temperature (° C.), avertical axis represents a relative vapor pressure (represented bylogarithm), and a raw material a of gas A, a raw material b of gas B,and a raw material c of gas C each represent a relative vapor pressureat each temperature. In addition, the gas A and the gas C arecomplex-forming gas, and the gas B is complex stabilizing material gas.Referring to FIG. 2, it is read that a ratio of a relative vaporpressure of the liquid raw material a of the gas A and a relative vaporpressure of the liquid raw material b of the gas B is 1:13 at 20° C.,1:5 at 50° C., and 1:4 at 80° C. That is, the mixing ratio of the gas Aand the gas B included in the mixed gas generated from the vaporizer 32can be adjusted to a range of 1:13 to 1:4 by filling the vaporizer 32with the mixed liquid of the liquid raw material a and the liquid rawmaterial b and adjusting an operating temperature of the vaporizer 32 tobe between 20 to 80° C. In addition, instead of the gas A, if thechemical liquid 30 including a mixture of the liquid raw material c ofthe gas C exhibiting characteristics similar to those of the gas A andthe liquid raw material b is used, it is understood that the mixedetching gas in which a mixing ratio of the gas C and the gas B is 5:4under, for example, the operating condition at 80° C. can be prepared.Even when the chemical liquid 30 includes three or more kinds ofcomponents as a raw material, it is possible to control the respectivemixing ratios by the same method.

Based on the principle, by selecting the combination of the gasificationraw material kinds and the operating condition of the vaporizer, themixed etching gas having a predetermined mixing ratio and predeterminedcharacteristics can be obtained even by the gas supply line 15 having asimple structure. It should be noted that not only the temperaturecontrol but also the pressure control or the combination of the pressurecontrol and the temperature control can be used as the operatingcondition of the vaporizer.

In addition, it is possible to not only use the mixed liquid of theplurality of raw materials as the chemical liquid 30, but also use asthe chemical liquid 30 an etching gas precursor substance in which apartial structure (function expressing partial structure) correspondingto the raw material for the complex-forming gas and a partial structure(function expressing partial structure) corresponding to the rawmaterial for the complex stabilizing material gas are bonded to therespective places of the same molecule. By vaporizing the etching gasprecursor substance with the vaporizer, the complex-forming gas and thecomplex stabilizing material gas are synchronously released from theetching gas precursor substance to obtain the mixed etching gasincluding the complex-forming gas and the complex stabilizing materialgas. When the etching gas precursor substance is used, it is possible toaccurately control the mixing ratio of the complex-forming gas and thecomplex stabilizing material gas to be generated by a chemical structureof the precursor. In general, since the vapor pressure is reduced when amolecular weight of a material is increased, it is preferable that themolecular weight of the precursor substance is small.

When the mixed chemical liquid 30 is used, it is preferable to include amixed chemical liquid composition adjustment unit 35 that continuouslymonitors the composition of the mixed chemical liquid 30 filled in thechemical liquid tank 31 and adjusts the composition according to theobtained monitoring result. FIG. 3 illustrates the semiconductormanufacturing apparatus including the peripheral units of the processingportion in addition to the processing portion illustrated in FIG. 1. Inorder to continuously monitor the composition of the mixed chemicalliquid 30, various kinds of non-destructive chemical liquidconcentration meters can be applied, and an infrared absorptiometer 300is preferably used. A case in which a mixed liquid of the liquid rawmaterial a of the gas A and the liquid raw material b of the gas B isused as the mixed chemical liquid 30 is described by way of example. Aninfrared absorption spectroscopy is performed on several types of mixedliquids having different mixture ratios of the liquid raw material a ofthe gas A and the liquid raw material b of the gas B in advance, acalibration curve is prepared in advance based on absorbency of at leasttwo kinds of wavelengths, which is stored in a composition detector 301.The composition detector 301 compares the measurement result of infraredabsorption intensity of the mixed chemical liquid 30 by the infraredabsorptiometer 300 with the calibration curve to obtain the compositionratio of the liquid raw material a of the gas A and the liquid rawmaterial b of the gas B included in the mixed chemical liquid 30.Specifically, a case in which the liquid raw material a is a chemicalsubstance having a carbonyl group in a molecule and the liquid rawmaterial b is a chemical substance that does not have the carbonyl groupbut has an ether group in a molecule will be described below. In thiscase, by the infrared spectroscopy, an infrared absorption peak showingstretching vibration of the carbonyl group appears in an area near1700±50 cm⁻¹, an infrared absorption peak showing stretching vibrationof the ether group appears in an area near 1000 to 1300 cm⁻¹, and thetwo infrared absorption peaks do not overlap each other and their peakintensity is changed according to the included concentration. Therefore,by performing the infrared absorption intensity spectroscopy on themixed chemical liquid 30, the peak intensity appearing in the area near1700±50 cm⁻¹ and the peak intensity appearing in the area near 1000 to1300 cm⁻¹ each reflect the concentration of the mixed chemical liquid 30of the liquid raw material a having the carbonyl group and theconcentration of the mixed chemical liquid 30 of the liquid raw materialb having the ether group. The same goes for the case of a mixed liquidof three or more kinds of materials.

In accordance with the result obtained by the composition detector 301monitoring the composition of the mixed chemical liquid 30, acomposition adjustment portion 302 performs adjustment of thecomposition of the chemical liquid 30 remaining in the chemical liquidtank 31, that is, an operation such as replenishment of deficientcomponents from a bottle 303 for the liquid raw material a and/or abottle 304 for the liquid raw material b.

It should be noted that in addition to an infrared spectrophotometerillustrated in FIG. 3, a simple analyzer of a specific gravity, arefractive index or the like may be installed in the chemical liquidtank 31 to simply monitor the composition. In addition, if impurities orforeign matters are mixed in the mixed chemical liquid 30, there is apossibility that the impurities or foreign matters are infiltrated intothe processing chamber 11 via the vaporizer 32 and the gas supply line15. Therefore, the mixing of impurities or foreign matters into themixed chemical liquid 30 should be avoided. In particular, when water(H₂O) is mixed in the mixed chemical liquid 30, since there is apossibility that remarkable deterioration of the etching performance ofthe mixed etching gas may occur, it is preferable for the compositiondetector 301 to strictly monitor the amount of moisture mixed in themixed chemical liquid 30.

Although not illustrated, a carrier gas supply system for adjusting asupply concentration of the mixed etching gas in addition to a systemfor supplying the mixed etching gas is also connected to the gas supplyline 15, and if necessary, the concentration of the mixed etching gassupplied into the processing chamber 11 can be adjusted within a rangeof 0 to 100%. As the carrier gas, general inert gas such as nitrogen orargon may be used.

In addition, vaporizers of a plurality of systems may be connected tothe gas supply line 15 in consideration of the complication of thestructure of the semiconductor device to be manufactured and thediversification of the high-k insulating film material to be etched.Furthermore, in the case where the vaporizers of the plurality ofsystems are installed, the chemical liquid 30 filled in each of thechemical liquid tanks 31 may be the mixed chemical liquid of theplurality of liquid raw materials or a single chemical stock solution.

(1) It is possible to easily adjust the mixing ratio of the mixedetching gas by vaporizing the single chemical stock solution in each ofthe vaporizers or the vaporizer of at least one system of the pluralityof systems. In addition, in the above example, in the case in whichfirst mixed etching gas of the gas A and the gas B is generated from avaporizer of a first system, etching gas of the gas C is generated froma vaporizer of a second system, the first mixed etching gas reacts on afirst high-k insulating film material, and second mixed etching gas inwhich the gas C is additionally mixed with the first mixed etching gasreacts on a second high-k insulating film material (which differs fromthe first high-k insulating film material in terms of rare earthelements included), the vaporizer of the first system is used when thefirst high-k insulating film layer of the semiconductor device is etchedand the vaporizers of the first system and the second system are usedtogether when the second high-k insulating film layer is etched, suchthat it is possible to easily etch different high-k insulating filmlayers having a plurality of materials included in the semiconductordevice.

(2) In the case in which the mixed chemical liquid is vaporized by eachof the vaporizers of the plurality of systems, in the above example, forexample, the vaporizer of the first system can generate the first mixedetching gas of the gas A and the gas B and the vaporizer of the secondsystem can generate third mixed etching gas of the gas C and the gas B.In this case, if both the first mixed etching gas and the third mixedetching gas react on the same high-k insulating film material, it isconsidered that the vaporizers of the first system and the second systemare used together to etch the predetermined high-k insulating film layerof the semiconductor device. In addition, when the first mixed etchinggas reacts on the first high-k insulating film material and the thirdmixed etching gas reacts on the second high-k insulating film material(which differs from the first high-k insulating film material in termsof rare earth elements included), the vaporizer of the first system isused when the first high-k insulating film layer of the semiconductordevice is etched and the vaporizer of the second system is switched andused when the second high-k insulating film layer is etched, such thatit is possible to easily etch different high-k insulating film layershaving the plurality of materials included in the semiconductor device.

The vacuum line 13 is provided with a cold trap 70 to prevent the mixedetching gas discharged as unreacted or a compound (volatileorganometallic complex) generated by the etching processing from leakingto the environment. The cold trap 70 is installed between the container10 and the opening/closing valve 14, between the opening/closing valve14 and the vacuum pump 17, and at one or more place in an exhaust systemof the vacuum pump 17 to cool and condense the unreacted etching gasdischarged together with the carrier gas from the processing chamber 11or the compound (volatile organometallic complex) generated by theetching processing. FIGS. 1 and 3 illustrate an example in which a firstcold trap 70 a is installed between the opening/closing valve 14 and thevacuum pump 17 and a second cold trap 70 b is installed in the exhaustsystem of the vacuum pump 17. The exhaust system of the vacuum pump 17is finally connected to an exhaust gas detoxifying facility 71 and extraetching gas, volatile organometallic complex or the like which cannot becold-condensed by the cold trap 70 are adsorbed and collected by anadsorbent to be removed. FIG. 3 illustrates the arrangement example inwhich the cold trap 70 b and the exhaust gas detoxifying facility 71 areconnected to the exhaust system of the vacuum pump 17 in series, but itis not limited to the arrangement example.

In order to beneficially utilize the chemical substances cold-condensedby the cold trap 70 and/or the exhaust gas detoxifying facility 71, acollecting and sorting device 72 decomposes the collected chemicalsubstances as they are or as needed to collect and sort valuablesubstances. Specifically, the mixed etching gas discharged as unreactedor the compound (volatile organometallic complex and the like) generatedby the etching processing is mixed and reacted with an acid treatmentliquid supplied from an acid treatment liquid bottle 73 in thecollecting and sorting device 72. By reacting the chemical substancescold-condensed by the cold trap 70 and the exhaust gas detoxifyingfacility 71 with the acid treatment liquid under appropriate conditions,some of the chemical substances are acid-decomposed, and the liquid rawmaterial a and the liquid raw material b included in the mixed chemicalliquid 30 can be separated and regenerated from the acid-decomposedchemical substances. The separated and regenerated liquid raw materialsa and b are collected to recovery bottles 74 and 75, respectively.

The acid treatment liquid used in the collecting and sorting device 72is a liquid obtained by dissolving a substantially nonvolatile acidicsubstance in a non-aqueous polar solvent having a boiling point >200° C.The acidic substance preferably is a substance having an aciddissociation constant pKa of 3 or less as an index representing acidityof the acidic substance (acidity is stronger as the pKa value issmaller). It is determined whether or not the mixed etching gas or thecompound recovered by the acid treatment liquid can be acid-decomposedbased on the raw material. Although the raw material suitable for thepresent embodiment is described below, these raw materials can beacid-decomposed if the pKa of the acidic substance is equal to or lessthan 3. By contrast, it is also possible to use an acidic substancehaving a lower acidity corresponding to the raw material if the acidicsubstance is selected according to the used raw material.

The collecting and sorting device 72 acid-decomposes the mixed etchinggas or the volatile organometallic complex generated by the etchingprocessing and the like, regenerates the raw material for thecomplex-forming gas and the raw material for the complex stabilizingmaterial gas, and recovers the raw material in a form of a solutiondissolved in the non-aqueous solvent. Further, a distillation deviceincluding a fractionator performs a distillation operation on thesolution of the non-aqueous solvent including the raw material for thecomplex-forming gas and the raw material for the complex stabilizingmaterial gas as a solute to fractionally distill the raw material forthe complex-forming gas and the raw material for the complex stabilizingmaterial gas. In order to simply perform the fractional distillation aspossible, a substance having a low boiling point is not used as thenon-aqueous solvent or the acidic substance. In addition, if aceticacid, hydrochloric acid or the like which is a volatile acidic substanceis used, there is a possibility that the separation is insufficient in arelatively simple fractionating device, for example, a fractionatingdevice having the theoretical plate number of 20 plates or less. In thismanner, in the case of using the low boiling point non-aqueous solventor the low boiling point acidic substance, the raw material for thecomplex-forming gas and the raw material for the complex stabilizingmaterial gas are insufficiently separated from the non-aqueous solventor the acidic substance only by the fractional distillation, such thatit is difficult to reuse the raw materials as they are or there are somerestrictions in reusing the raw materials. In addition, if an aqueoussolvent, alcohol or the like is used instead of the non-aqueous solvent,the regenerated raw material for the complex-forming gas and the rawmaterial for the complex stabilizing material gas react with the aqueoussolvent, the alcohol or the like, and therefore there is a possibilitythat the collected amount is decreased. For this reason, it ispreferable to use the non-aqueous solvent as the solvent of the acidtreatment liquid.

Specific examples of the non-aqueous polar solvent having a boilingpoint of higher than 200° C. may include tetramethylene sulfone(sulfolane), dimethylimidazolidinone, triglyme and the like. Inaddition, specific examples of the acidic substance having pKa<3 mayinclude toluenesulfonic acid, methanesulfonic acid, phosphoric acid andthe like. In contrast, there is a problem in that a fractionatingdistillation of volatile acids such as hydrochloric acid, nitric acidand formic acid becomes complicated as described above.

In order to recover and reuse the raw material, it is preferable torecover the chemical substances without impurities. From this viewpoint,when there is a possibility that impurities derived from the vacuum pumpare mixed into the exhaust system of the vacuum pump 17, only chemicalsubstances cold-condensed by the cold trap 70 a installed in front ofthe vacuum pump 17 may be a recovery target of a raw material, andothers may be discarded. In addition, the cold trap 70 a is disposed infront of the vacuum pump 17 to prevent the chemical substances frombeing mixed into the vacuum pump 17. When the chemical substancescold-condensed by the cold trap 70 b installed in the exhaust system ofthe vacuum pump 17 or the exhaust gas detoxifying facility 71 arediscarded, it is allowable to use the aqueous solvent or the alcoholinstead of the non-aqueous solvent.

Next, a description will be given of a semiconductor manufacturingmethod performed by the semiconductor manufacturing apparatus in FIG. 1or 3. The processing in the semiconductor manufacturing apparatus iscontrolled by a control device 100.

First, a wafer conveyance device (not illustrated) conveys thesemiconductor substrate (wafer) 1 into a desired position on the waferstage 12 disposed in the processing chamber 11 through the waferconveyance port 20 installed in the container 10. The conveyedsemiconductor substrate 1 is adsorbed and fixed by a gripping force ofthe wafer stage 12. The high-k insulating film and a resist film or ahard mask film having an opening pattern at a desired place are formedon the semiconductor substrate 1 in advance. FIG. 4 illustrates anexample of a cross-sectional view of the semiconductor substrate (wafer)1. A high-k insulating film 4 is formed on a silicon oxide (SiO₂) film 3formed on a silicon (Si) substrate 2, and a hard mask 5 having a desiredgate electrode pattern shape is further formed on the high-k insulatingfilm 4. The high-k insulating film 4 is, for example, a lanthanum oxide(La₂O₃) film or a hafnium oxide (HfO₂) film. First, after the lanthanumoxide (La₂O₃) film or the hafnium oxide (HfO₂) film is formed by theknown sputtering method, physical vapor deposition (PVD) method, atomiclayer deposition (ALD) method, chemical vapor deposition (CVD) methodand the like, heat treatment of about 500 to 1000° C. is performed toobtain a desired film quality. To process the lanthanum oxide film orthe hafnium oxide film to have a desired gate electrode pattern shape,the hard mask film 5 and a photoresist film are sequentially formed onthe formed high-k insulating film 4, a desired pattern is transferred tothe photoresist film using a photolithography technology, and the hardmask 5 is processed using the resist pattern as a mask to expose a partof the high-k insulating film 4. FIG. 4 illustrates a state in which theremaining resist pattern is removed thereafter. It should be noted thata semiconductor layer formed on the semiconductor substrate (wafer) 1 isnot limited to the example of FIG. 4. For example, an insulating layerformed under the high-k insulating film 4 may be a silicon nitride (SiN)film. The semiconductor manufacturing apparatus of the presentembodiment removes an exposed part 6 by selective etching. In thisselective etching, a non-plasma-like dry etching technology as describedbelow is applied. FIG. 5 schematically illustrates a surface temperaturecycle of the semiconductor substrate in the etching process of thepresent embodiment. It should be noted that FIG. 5 is illustrated toeasily understand points of temperature control in the etching processof the present embodiment, in which an actually generated temperature, atemperature gradient, or a necessary control time becomes differentdepending on a kind of material to be etched, a kind of complex-formingmaterial, a structure of a semiconductor device and the like.

After the semiconductor substrate 1 is fixed on the wafer stage 12, theinsides of the container 10 and the processing chamber 11 aredecompressed, the semiconductor substrate 1 is heated while beingdecompressed, and gases (water vapor and the like) or foreign mattersadsorbed on the surface of the semiconductor substrate 1 are desorbed(period (a)). After it is confirmed that the desorption of the gascomponent adsorbed on the surface of the semiconductor substrate 1 isalmost completed based on a display by an indication of a pressure gaugeinstalled in the container 10 or the processing chamber 11, the heatingof the semiconductor substrate 1 is stopped while the semiconductorsubstrate 1 being decompressed and cooling is started (period (b)). Anyknown means can be used for the heating/cooling. However, sinceprocessing of temperature rising or heat releasing (temperature falling)as described below is performed plural times, a heating/coolingmechanism suitable for rapid heating or rapid cooling is preferable. Forexample, it is preferable to control the surface temperature of thesemiconductor substrate 1 to rapidly reach a desired temperature bycombining a lamp type heating mechanism such as a halogen lamp or axenon lamp and a pusher pin mechanism lifting up the semiconductorsubstrate 1 from the wafer stage 12. It should be noted that when thelamp type heating is performed, there is a need to select a wavelengthof a lamp type heating light source by evaluating a behavior of theorganometallic complex generated during the etching with respect tolight. In other words, the organometallic complex generated by thereaction of the high-k insulating film 4 with the complex-forming gasand the complex stabilizing material gas may be decomposed by lightirradiation. For this reason, it is necessary to select the irradiationwavelength by evaluating a decomposition resistance of theorganometallic complex against light in advance. Since theorganometallic complex generated by the reaction of the high-kinsulating film with the complex-forming gas and the complex stabilizingmaterial gas shows a light absorption behavior peculiar to theorganometallic complex called metal to ligand charge transfer spectrum,there is a need to prevent light near the wavelength band from beingirradiated. Meanwhile, since the organometallic complex also hasproperty of efficiently absorbing light of a specific wavelength bandand converting the light into heat, rapid heating can be performed byusing a light source emitting light of the wavelength band. In general,since the metal to ligand charge transfer spectrum is often in awavelength band of 350 nm or less, it is preferable to block the lightin the wavelength band of 350 nm or less when the lamp type heating isperformed. Meanwhile, generally, the organometallic complex has a highabsorption efficiency of infrared light in a range of 2 to 10 μm.Therefore, for example, a halogen lamp installed with ayellow-cut-filter in order not to emit light including so-calledultraviolet light of 400 nm or less is used as a light source.

It should be noted that since the heating in the period (a) is to desorbthe gases or foreign matters adsorbed on the surface, it is alsopossible to apply the known methods other than the heating. In addition,these methods may be used together with the heating processing.

The temperature of the semiconductor substrate 1 is lowered until itfalls below temperature T₁ (hereinafter, referred to as a gasintroduction upper limit temperature T₁). Thereafter, the mixed etchinggas is introduced into the processing chamber 11 together with thecarrier gas through the gas supply line 15 to be in contact with thesurface of the semiconductor substrate 1, and the molecules of thecomplex-forming gas or the molecules of the complex stabilizing materialgas included in the mixed etching gas are physically adsorbed on thesurface of the semiconductor substrate 1 (period (c)).

Here, if the mixed etching gas is introduced into the processing chamber11 in a state where the temperature of the semiconductor substrate 1exceeds a predetermined gas introduction upper limit temperature T₁, thereaction of the high-k insulating film 4, for example, the lanthanumoxide film with the mixed etching gas partially proceeds quickly.Therefore, the etching performed in a lateral direction from the hem ofthe resist pattern, a so-called side etching, is performed, or defectssuch as susceptibility to influence of concentration irregularity of themixed etching gas or strong revelation of a micro loading effect tend tooccur. Further, the mixed etching gas reacts with a material other thanthe high-k insulating film 4, for example, a resist material or anothermetal film, silicon of the semiconductor substrate 1, or silicon oxideor the like, such that there is a possibility that the desired processedshape and desired characteristics cannot be obtained. To minimize theoccurrence of the defects, the mixed etching gas is introduced into theprocessing chamber 11 after waiting until the temperature of thesemiconductor substrate 1 falls below the predetermined gas introductionupper limit temperature T₁.

The upper limit of the temperature at which the mixed etching gas isintroduced into the processing chamber 11 is influenced by variousfactors such as the dimension of the wafer 1, the material of the wafer,the film structure/film composition of the high-k insulating film, thecomposition of the mixed etching gas, and the film thickness or theopening dimension of the resist film or the hard mask film. For thisreason, there is a need to check and set the gas introduction upperlimit temperature T₁ beforehand for each semiconductor device to beprocessed.

After the temperature of the semiconductor substrate 1 in a state wherethe mixed etching gas is physically adsorbed on the surface of thehigh-k insulating film slowly rises by slow heating while beingmaintained not to exceed 200° C. even at the place where the temperatureis highest in the semiconductor substrate 1 and then is maintained at apredetermined temperature T₂ for a certain time (period (d)), the rapidtemperature rising to the highest temperature of 500° C. is performedwhile only the carrier gas (mixed etching gas concentration is zero) issupplied through the gas supply line 15 (period (e)). In the meantime, abalance between a supply rate of the mixed carrier gas supplied throughthe gas supply line 15 and an exhaust rate of the carrier gas exhaustedthrough the vacuum line 13 is adjusted to maintain an appropriatelydecompressed state.

The molecules of the complex-forming gas and the molecules of thecomplex stabilizing material gas which are the components of the mixedetching gas are hopping diffused while being physically adsorbed on thesurface of the semiconductor substrate 1 during the slow heating, suchthat the adsorption density (adsorption amount per unit surface area) onthe surface of the semiconductor substrate 1 is uniform. In the period(d), to prevent the transition from the physical adsorption state to thechemical adsorption state before the adsorption density of the moleculesof the complex-forming gas and the molecules of the complex stabilizingmaterial gas on the substrate surface reaches the uniform state, thereis a need to control the processing conditions such as the temperature,the time, and the pressure and the optimization of the processingconditions for each semiconductor device to be manufactured isperformed.

It should be noted that since the purpose of setting the period (d) isto uniformize the density at which the molecules of the complex-forminggas and the molecules of the complex stabilizing material gas areadsorbed on the surface of the semiconductor substrate 1, the period (d)may be unnecessary as long as the sufficient uniformity of processingaccuracy can be realized in the period (period (c)) in which the mixedetching gas is introduced. Alternatively, only the slow heating may beperformed.

After the in-plane uniformity of the adsorption density is achieved bythe slow heating, the rapid heating and temperature rising are performedwhile only the carrier gas in which the concentration of the mixedetching gas is zero is supplied (period (e)). In the earliest stage ofthe rapid heating and temperature rising, the chemical reaction isgenerated between the molecules of the complex-forming gas and themolecules of the complex stabilizing material gas included in theetching gas and the outermost molecular layer of the high-k insulatingfilm 4 of the semiconductor substrate 1. The material of the high-kinsulating film 4 is selected so as to conform to specifications andcharacteristics of the device to be manufactured, and is, for example,an oxide film including metal elements classified in a fifth period suchas Y, Zr, La, Hf, and Ta and the following periods of the periodic tableof elements. In the chemical reaction, the molecules of thecomplex-forming gas and the molecules of the complex stabilizingmaterial gas react with the high-k insulating film 4 to be convertedinto the molecules of the volatile organometallic complex including themetal elements included in the high-k insulating film 4. The reaction ofthe metal elements included in the high-k insulating film with themolecules of the complex-forming gas and the molecules of the complexstabilizing material gas adsorbed on the high-k insulating film 4 in thephysically adsorbed state proceeds at an interface therebetween, and onelayer on the outermost surface of the high-k insulating film 4 isconverted into the organometallic complex. If one layer on the outermostsurface of the high-k insulating film 4 is converted into theorganometallic complex, the generated organometallic complex preventsthe direct contact of the molecules of the complex-forming gas and thehigh-k insulating film 4 to suppress the reaction to increase the filmthickness due to the additional generation of the organometalliccomplex. Therefore, if the film thickness of the organometallic complexreaches the film thickness corresponding to the film thickness generatedby converting one layer of the outermost surface of the high-kinsulating film 4 into the organometallic complex, the reaction toconvert the high-k insulating film 4 into the organometallic complex issubstantially stopped.

After the outermost surface layer of the high-k insulating film 4 isconverted into the organometallic complex in the earliest stage of therapid heating and temperature rising, if the temperature of thesemiconductor substrate 1 further rises to reach near the boiling pointsof each of the complex-forming gas and the complex stabilizing materialgas which are the components of the mixed etching gas, the molecules ofthe complex-forming gas and the molecules of the complex stabilizingmaterial gas which are physically adsorbed on the surface of thesemiconductor substrate 1 cannot maintain the physically adsorbed stateto start to be desorbed from the surface of the semiconductor substrate1 and are swept away by the carrier gas flow to be removed from thesurface of the semiconductor substrate 1. While the removal of thecomplex-forming gas and the complex stabilizing material gas which arein the physically adsorbed state is progressed, since the latent heat ofvaporization of the complex-forming gas and the complex stabilizingmaterial gas is deprived, the surface temperature of the semiconductorsubstrate 1 does not rise (temperatures T₃ and T₄). Since theorganometallic complex has a boiling point higher than that of thecomplex-forming gas and the complex stabilizing material gas, theorganometallic complex is not desorbed at this point.

When the molecules of the complex-forming gas and the molecules of thecomplex stabilizing material gas which are in the physically adsorbedstate on the surface of the semiconductor substrate 1 are completelyremoved, the surface temperature of the semiconductor substrate 1rapidly rises, but if the temperature reaches near a volatilizationpoint (boiling point or sublimation point) of the organometalliccomplex, the molecules of the organometallic complex starts to bedesorbed from the high-k insulating film 4 on the surface of thesemiconductor substrate 1. At this time, since the components derivedfrom the complex stabilizing material gas are included in the moleculesof the organometallic complex, the organometallic complex isdesorbed/volatilized from the surface of the high-k insulating film 4without being decomposed and is swept away by the carrier gas flow to beremoved from the surface of the semiconductor substrate 1. In theexample of FIG. 5, in order to completely remove the organometalliccomplex converted from the high-k insulating film 4, the temperaturerapidly rises to the highest attainment temperature of 500° C., but itis preferable to appropriately adjust the highest attainment temperatureaccording to the kind of high-k insulating film and the composition ofthe organometallic complex converted therefrom. It should be noted thatsince the change in temperature at the time of the desorption of theorganometallic complex is determined by the balance between heatgeneration by a chemical bond cleaving reaction and the absorption bythe latent heat of evaporation, it does not mean that the temperaturerises simply as illustrated in FIG. 5.

By this series of processes, after the outermost surface layer of thehigh-k insulating film 4 is converted into the organometallic complex,the organometallic complex is removed from the surface of thesemiconductor substrate 1, and the high-k insulating film 4 in a statewhere the high-k insulating film 4 is thinned by the thicknesscorresponding to one layer of the outermost surface layer of the high-kinsulating film 4 is exposed again.

Thereafter, after the temperature of the semiconductor substrate 1 islowered until it falls below the gas introduction upper limittemperature T₁ (period (f)), processing in periods (c) to (f), that is,a series of processing such as the introduction of the mixed etching gasthrough the gas supply line 15, the uniformity in the surface of thesubstrate by the slow heating, the generation of the organometalliccomplex, the discharge of the excess part of the mixed etching gas bythe rapid heating under the decompression, and the volatilizationremoval of the organometallic complex are repeated up to the desiredetching depth, such that the isotropic dry removal of the high-kinsulating film 4 is completed.

Since the complex-forming gas included in the mixed etching gas reactsonly with a specific oxide or a specific halide and does not react withsubstances having other molecular structures such as a nitride, anetching selective ratio of the oxide to the nitride is kept high. Forexample, the high etching selective ratio for a silicon nitride (SiN)film or a titanium nitride film (TiN) which is often used in thesemiconductor device is exhibited. Further, in the complex stabilizingmaterial gas included in the mixed etching gas, the complex stabilizingeffect for the metallic complex made of metal elements of the fourthperiod and before the fourth period of the periodic table of elements isnot high. For this reason, even when the organometallic complex isgenerated from an oxide (for example, a silicon oxide (SiO₂) film) andthe like other than the high-k insulating film 4, the organometalliccomplex does not have high volatility, or the volatility is notefficiently removed as the organometallic complex is thermallydecomposable. Therefore, the high etching selective ratio is exhibitedbetween the high-k insulating film and other oxide films.

The details of all the conditions such as the composition ratio of thecomplex-forming gas and the complex stabilizing material gas which areincluded in the mixed etching gas, the supply concentration, the supplytime, the temperature of the semiconductor substrate 1 at the time ofthe supply, the time until the temperature rises after the mixed etchinggas is supplied need to be appropriately adjusted by the material or thethickness of the high-k insulating film 4 formed on the semiconductorsubstrate 1, the micro structure of the device and the like. As ageneral tendency, the etching rate of the mixed etching gas suppliedtogether with the carrier gas tends to be getting faster as theconcentration of the mixed etching gas to the carrier gas is high. Forthis reason, in the etching processing of a deep hole trench or a highaspect pattern, it is preferable to gradually change the componentcomposition or the supply concentration of the mixed etching gassupplied. For example, at the initial stage, the mixed etching gas issupplied at a low concentration, the concentration of the mixed etchinggas is gradually increased, and the mixed etching gas having aconcentration of 100% is finally supplied. As described above, after theinfluence of the component composition, the supply concentration, andthe supply time of the mixed etching gas, and the substrate temperatureis checked, the appropriate processing conditions are determined.

The etching mechanism as described above makes it possible to adopt thevaporizer having a simple configuration like a bubbling type in thesemiconductor manufacturing apparatus of the present embodiment. Theratio of the complex-forming gas and the complex stabilizing materialgas in the mixed etching gas can be determined by the chemical structureof the organometallic complex to be generated, and even if the ratiobetween the complex-forming gas and the complex stabilizing material gasis deviated, it does not directly affect the etching performance. Inaddition, although the materials for the complex-forming gas and thecomplex stabilizing material gas will be described later, both of themare organic compounds which are liquid at a normal temperature and havea relatively high vapor pressure. Therefore, the limitation of thecontrol accuracy and the restriction of the supply flow rate which havebeen the problems of the bubbling type vaporizer are not a big problemin the semiconductor manufacturing apparatus of the present embodiment.Rather, as has been conventionally done to supply two or more kinds ofgases to the semiconductor manufacturing apparatus, in a system in whichseparate chemical liquid tanks and vaporizers are installed for each gascomponent to individually gasify these gas components and a gas mixermixes each gas component such that the gas components have a specificcomposition ratio, the problems of increasing the size of thesemiconductor manufacturing apparatus, increasing the number of partsand the like tend to be actualized as the number of kinds of mixed gasesis increased. In the meantime, in the case of adopting the bubbling typevaporizer, since the discrepancy in the mixing ratio between thecomplex-forming gas and the complex stabilizing material gas due to thelow control accuracy of the vaporizer leads to a waste of the rawmaterial, as illustrated in FIG. 3, the collecting and sorting device ispreferably installed to recover the extra raw material.

Next, the raw material for the complex-forming gas which is thecomponent for converting the high-k insulating film into the volatileorganometallic complex and the raw material for the complex stabilizingmaterial gas which is the component for increasing the stability of thevolatile organometallic complex are described.

The fact that the mixed etching gas of the complex-forming gas and thecomplex stabilizing material gas is generated by vaporizing the chemicalliquid 30 filled in the chemical liquid tank 31 installed in the gassupply line 15 by the vaporizer 32 was described with reference toFIG. 1. In addition, the chemical liquid 30 is a raw material forgenerating at least two kinds of gaseous component substances, namely,the complex-forming gas and the complex stabilizing material gas, and isthe mixed liquid including the raw material for the complex-forming gasand the raw material for the complex stabilizing material gas.

From the viewpoint of the operability and the work efficiency of theprocess of vaporizing the chemical liquid 30, both of the raw materialfor the complex-forming gas and the raw material for the complexstabilizing material gas are selected from materials of which theboiling point at 1 atm does not largely exceed approximately 200° C.

The raw material for the complex-forming gas is an organic compoundcapable of forming at least two or more coordination bonds to atransition metal atom, that is, a so-called multidentate ligandmolecule. Preferably, there are diketones or ketoester (including twoC═O bonds), ketoimine (including C═O bond and C═N bond) and the like.Specific examples of the substance names may include acetylacetone,trifluoroacetylacetone, trifluorophenyl butadione,hexafluoroacetylacetone, dipivaloylmethane, thenoyltrifluoroacetone,trifluorofurylbutadione, dimethylheptafluorooctadione and the like.

In addition, the raw material for the complex stabilizing material gasis an organic compound having two or more elements having an unsharedelectron pair such as an oxygen atom or a nitrogen atom in the molecularskeleton thereof, preferably, five or more atoms except for a hydrogenatom and a fluorine atom. For example, FIG. 6 illustrates a molecularstructure of dimethoxyethane. The dimethoxyethane has six atoms 51 to 56excluding hydrogen atoms and fluorine atoms.

An action and an effect of the complex stabilizing material gas aredescribed with reference to FIG. 7. The ligands of a transition metalatom (for example, lanthanum (La)) 61 and complex-forming materials 62 ato 62 c in the high-k insulating film are coordinate bonded to form theorganometallic complex. By including the complex stabilizing materialgas in the etching gas, an element having an unshared electron pair inthe molecule of a complex stabilizing material 63 (for example, oxygenin 12-crown-4 molecules in FIG. 7) is weakly bonded to the transitionmetal to cancel the coordinative unsaturation of the transition metalatom, thereby increasing the binding stability of the organometalliccomplex. Further, the complex stabilizing material has a relativelylarge molecular cross-sectional area to prevent oxygen molecules, watermolecules or the like from approaching a central nucleus of theorganometallic complex due to the steric hindrance. It is possible toincrease the stability of the organometallic complex by thesemultifunctions.

The raw material for the complex stabilizing material gas is preferablyethers. The ethers are suitable as the raw material for the complexstabilizing material gas from the viewpoint that they do not cause thechemical reaction with the raw material for the complex-forming gas aslisted above. A specific example of the substance name for some of thesubstances may include a straight chain ether such as dimethoxyethane,diethylene glycol dimethyl ether, and propylene glycol dimethyl ether,cyclic ether such as tetrahydrofuran, 12-crown-4, and diaza-12-crown-4,adiponitrile, succinonitrile and the like.

In the case of using hexafluoroacetylacetone (liquefied diketonecompound) as the raw material for the complex-forming gas and diethyleneglycol dimethyl ether (liquid ether with straight chain) previouslydehydrated as the raw material for the complex stabilizing material gas,metal oxides (metal oxides including rare earth elements) includinggroup 3A metals such as lanthanum (La) or yttrium (Y) has highreactivity without reacting with a silicon oxide (SiO₂) film, metal suchas silicon (Si), stainless steel (SUS), copper (Cu), and tungsten (W), anitride film such as a titanium nitride (TiN) film or a silicon nitride(SiN) film, and metal fluorides such as yttrium fluoride (YF₃). Anexample thereof is illustrated in FIG. 8. The reaction rate is obtainedas a mass ratio of the substance lost by being volatilized by thereaction of the mixed etching gas (complex-forminggas:hexafluoroacetylacetone, complex stabilizing material gas:diethyleneglycol dimethyl ether) with the substance with respect to a mass of asubstance before the reaction. By doing so, it was confirmed that themixed etching gas of the present embodiment selectively reacts with thehigh-k insulating film material to generate the volatile organometalliccomplex, which is selectively removable under the decompression andheating.

In addition, when the high-k insulating film material and thecomplex-forming gas react with each other without the complexstabilizing material gas, the defect that residues are caused during theprocess of desorbing and volatilizing the organometallic complex fromthe surface of the high-k insulating film material is caused. Theseresidues were a carbon-based impurity generated by decomposing theorganometallic complex. Therefore, during the process of the slowheating illustrated in FIG. 5 (period (d)), it is necessary to set theconditions such that the adsorption concentration of the complexstabilizing material gas as well as the complex-forming gas is alsouniform in the surface of the semiconductor substrate 1.

What is claimed is:
 1. A method for manufacturing a semiconductordevice, the method comprising: placing, in a processing chamber, asemiconductor substrate on which a mask layer having a predeterminedpattern shape is formed on a high-k insulating film; desorbing gas or aforeign matter adsorbed on a surface of the semiconductor substrate;supplying reactive gas to the processing chamber in a state where atemperature of the semiconductor substrate falls below a predeterminedtemperature; stopping the supply of the reactive gas and heating thesemiconductor substrate; and vaporizing an organometallic complexgenerated by reacting with a metal element included in the high-kinsulating film and exhausting the vaporized organometallic complex fromthe processing chamber, wherein the reactive gas is mixed gas includingcomplex-forming gas forming the organometallic complex by reacting withthe metal element included in the high-k insulating film and complexstabilizing material gas that increases stability of the organometalliccomplex.
 2. The method according to claim 1, wherein the metal elementincluded in the high-k insulating film is a metal element classified ina fifth period and the following periods of a periodic table.
 3. Themethod according to claim 1, wherein the metal element included in thehigh-k insulating film is a rare earth element.
 4. The method accordingto claim 1, wherein a raw material for the complex-forming gas is anorganic compound capable of forming at least two or more coordinationbonds to a transition metal atom, that is, a so-called multidentateligand molecule.
 5. The method according to claim 4, wherein the rawmaterial for the complex-forming gas includes any of diketones,ketoester, and ketoimine.
 6. The method according to claim 1, wherein araw material for the complex stabilizing material gas is an organiccompound having two or more elements having an unshared electron pairsuch as an oxygen atom or a nitrogen atom in a molecular skeleton andfive or more atoms except for a hydrogen atom and a fluorine atom. 7.The method according to claim 6, wherein the raw material for thecomplex stabilizing material gas is ethers.